The main purpose of a beamformer arrangement is to process acoustic signals in such a way, that signals from a preferred direction are enhanced with respect to signals from other directions. In this way, the signal quality of signals originating from a wanted sound source can be enhanced while noise, originating from different positions or directions of arrival, is reduced or even completely cancelled.
Such systems, an example is known from EP 1 640 971, are used, for instance, for hands-free communication in vehicles, such as voice control or hands-free telephony.
In order to align a beamformer arrangement with a certain preferred direction, the beamformer arrangement usually comprises a microphone array. For each microphone in the microphone array a time delay has to be determined. This time delay originates from a signal propagation delay due to the relative positioning of a wanted sound source with respect to the microphones in the microphone array. By compensating for this time delay and subsequently beamforming the time delay compensated signals, e.g. by weighting and summing of the signals, the beamformer arrangement is aligned with a certain preferred direction.
In general, the position of a wanted sound source and hence the direction of arrival of the acoustic signal, are a function of time. Hence, a re-calculation of time delays is necessary, as an estimate for the position of the wanted sound source varies, e.g. as a speaker moves. Already small variations in the direction of arrival of the acoustic signal will lead to a re-determination of the time delay. This frequent re-calculation is computationally inefficient.